linux-kernel - Re: [PATCH] mm: fix page_lock_anon

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Message-ID: <BANLkTinoFnTjCDL8B2HEYdYHqbMgCw_RrQ@mail.gmail.com>
Date:	Sat, 28 May 2011 16:56:11 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Hugh Dickins <hughd@...gle.com>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH] mm: fix page_lock_anon_vma leaving mutex locked

On Sat, May 28, 2011 at 4:24 PM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> That said, I do agree with the "anon_vma_root" part of your patch. I
> just think you mixed up two independent issues with it: the fact that
> we may be unlocking a new root, and the precise check used to
> determine whether the anon_vma might have changed.

Thinking some more about it, I end up agreeing with the whole patch.
The "page_mapped()" test is what we use in the slow-path after
incrementing the anon_vma count too when the trylock didn't work too,
so it can't be too wrong.

So I'm going to apply it as-is as an improvement (at least we won't be
unlocking the wrong anon_vma root), and hope that you and Peter end up
agreeing about what the sufficient test is for whether the anon_vma is
the right one.

                             Linus
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